Tension-spring return rotary valve actuator

ABSTRACT

A rotary valve actuator with movable actuator linkage maintained in a constant &#34;pull-pull&#34; tension, includes a sliding canister, rotatable lever, and a return spring substantially aligned in-line with each other. The linear motion of the canister in response to an expanding and contracting pressurized bladder is converted through chain linkage into rotary lever motion. The return spring is connected through respective chain linkage to the lever so the pulling tension of the spring/lever linkage rotates the lever and maintains tension on both chain linkages. Adjustable travel stops are provided. In an alternate embodiment the return spring chain linkage is configured at right angles to the linear movement of the canister.

This invention relates generally to fluid flow control devices and inparticular to actuators for fluid flow valves.

BACKGROUND OF THE INVENTION

A variety of fluid flow control valves and corresponding valve actuatorsare utilized for on/off control or throttling the flow of fluid, such asin a gas or oil pipeline system, or in other process fluid systems. Thefluid flow control valves are typically sliding stem control valves orrotary action control valves and are operated by a valve actuator suchas a pneumatic piston or diaphragm actuator responding to the output ofa valve positioner or valve controller instrument for accuratethrottling control of the valve.

In the case of rotary action control valves, these units typicallyemploy a flow control member in the form of a rotatable ball, rotatableball segment, or a rotatable butterfly element. The rotation of the flowcontrol element opens and closes the valve gate or plug.

Valve actuators for controlling such rotary action control valvestypically employ a movable diaphragm connected to a rod at the diaphragmcenter. Moving the diaphragm displaces the rod linearly and thusrequires a linear to rotary action translation. A rotational link armhas one end fixed to the valve rotary shaft and the other link arm endis coupled to the diaphragm rod. Linear movement of the diaphragm rodmoves the link arm and thereby actuates a rotational movement in thevalve shaft which is ultimately connected to the rotatable flow controlelement in the fluid control valve.

Such presently available rotary valve actuators employ many components,several of which require time consuming and expensive machining duringmanufacture. A manufacturer and users of rotary valve actuatorstherefore must inventory a large number of parts, and also mustinventory an increasing number of expensive, machined spare parts forrepair and replacement.

It is desired therefore to reduce the number of parts as well as toreduce the number of time consuming and expensive machined parts in arotary valve actuator so as to thereby reduce manufacturing costs andinventory requirements both for the manufacturer and the user. Inaddition, it is further desired to provide a rotary valve actuator ofreduced size and weight, and one having the capability of actuating avariety of rotary valves to reduce the number of rotary valve actuatorsrequired.

SUMMARY OF THE INVENTION

In accordance with the principles of the present invention, there isprovided a rotary valve actuator with movable actuator linkagemaintained in a constant "pull-pull" tension. A rotary valve actuator ofthe present invention includes a sliding cylinder or canister operatedby a pressurized bladder, enabling a rolling diaphragm bladder action tolinearly move the sliding canister. A cylindrical shaped lever isattached by a flexible canister/lever linkage to the sliding canister onone side of the lever. The linear motion of the sliding canister and theresulting pulling tension of the canister/lever linkage is convertedinto a rotary motion of the lever about its cylindrical axis.

Opposed to the sliding canister and on the other side of the rotatablelever there is provided a return spring which is attached to the leverwith a flexible spring/lever linkage. The spring is precompressed to apredetermined load so the pulling tension of the spring/lever linkagetends to rotate the lever in the direction of the spring, and at thesame time pull an unoperated sliding canister towards the lever andagainst an adjustable, canister bottom travel stop.

When the pneumatic pressure is introduced into the bladder, the pressurewill force the sliding canister away from the lever and thereby rotatethe lever in the direction of the sliding canister. The top travel ofthe sliding canister is restricted by an adjustable, canister top travelstop that is aligned with a stop pawl extending from the lever. As thelever rotates, it comes into contact with the stop. As the slidingcanister rotates the lever, this causes the spring to compress andresist the pull from the sliding canister. When the pressure is releasedfrom the bladder, the spring pulls the sliding canister back downagainst the canister bottom travel stop.

The respective linkage between the lever and the sliding canister on oneside, and between the lever and the spring on the other side of thelever can be flexible or rigid in nature. Flexible linkage can be formedfor instance of chain material, cables, etc. Rigid linkages can beformed of linked bars, rack and pinion members, etc. When using flexiblelinkage, the lever arm length is always the same distance from thecenter of the lever arm through its 90° rotation. In contrast, withrigid linkage, the lever arm length is reduced by 30° at the end of thelever arm travel. Also, the flexible linkage produces constant torquethrough the 90° rotation of the lever and is desired over rigid linkagewhich produces variable torque throughout the lever rotation.

A significant advantage is provided by the mounting of the rotatinglever intermediate the sliding canister on one side and the returnspring on the other side of the lever in a "pull-pull", constant tensionconfiguration. With the spring being mounted separately from the slidingcanister, this enables the lever arm to be shorter for the spring ascompared to the lever arm for the sliding canister. A shorter lever armreduces the spring travel and in turn reduces the spring height, makingthe actuator profile smaller, the actuator weight lighter, and theactuator construction less costly.

The pull-pull, constant tension valve actuator configuration of thepresent invention continually takes any lost motion out of the linkageconnecting the sliding canister cylinder, rotating lever, and returnspring. In contrast, in normal linkage configurations in actuators,continuous cycling of the movable actuator components causes wear andeventually an undesired lost motion condition is exhibited. In thepresent invention the pull-pull, constant tension feature between thesliding canister and the spring with the intermediate rotating lever notonly eliminates the lost motion problem of prior actuators, but alsoeliminates the need for precision mated parts, since all mating partsare kept in tension.

In a preferred embodiment of the present invention, the sliding canisterand spring are spaced 180° apart, in-line and resisting each otherthrough the connecting linkage. The tension forces transmitted throughthe linkage of the sliding canister to the lever and from the lever tothe spring linkage minimizes the load on the lever bearings and therebyminimizes bearing wear. Also, with the linkage in tension, the actuatorhousing is placed in compression, and the housing material incompression is more desirable than in tension. Also, with the housingmaterial parts in compression only a minimum number of fasteners arerequired for reliably maintaining the housing parts assembled.

A return spring, spring end caps and spring linkage is preassembled toform a spring cartridge. The spring cartridge can then be mounted in thehousing as a unitary unit. This insures that the spring linkage is notdamaged when preloading the spring and insures good linkage alignmentwith the lever and also reduces user safety issues during assembly ofthe actuator components.

The linkage between the lever and the sliding canister is connected atthe side wall of the sliding canister thereby simplifying the over allassembly. This connection reduces the number of parts required to carrythe pulling load to the rotatable lever thereby reducing actuator size,weight and cost.

A valve positioner or a valve controller instrument is mountabledirectly onto the actuator. The use of a sliding canister enables theease of providing manifolding air passageways from the bladder unit tothe direct mounted valve positioner, which eliminates the need forexterior tubing interconnecting the positioner and actuator units.

In an alternative embodiment of the pull-pull, constant tension rotaryvalve actuator of the present invention, the return spring is mounted90° to the center line of the sliding canister, with the same rotatablelever as in the prior mentioned in-line actuator embodiment. Thisalternative 90° embodiment of the pull-pull actuator of the presentinvention provides a more compact profile configuration than the in-lineembodiment, and may be preferred for use with certain valve situations.The same pressure actuated bladder, sliding canister, rotating lever,and spring cartridge are utilized as in the in-line embodiment. Also,the same advantages of the in-line rotary actuator embodiment areobtained by this alternative 90° rotary actuator embodiment, except thatbecause the spring is positioned 90° to the center line of the slidingcanister, this tends to create a diagonal load on the lever bearings,which diagonal bearing load is not present in the in-line embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of this invention which are believed to be novel are setforth with particularity in the appended claims. The invention may bebest understood by reference to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals identify like elements in the several figures and in which:

FIG. 1 is an elevational view, partly sectional, illustrating a rotaryvalve actuator constructed in accordance with the principles of thepresent invention, and with a canister cover at one end fragmented and aspring cartridge cover at the other end removed for convenience ofillustration;

FIG. 2 is a right side elevational view, partly sectional, of FIG. 1illustrating the rotary valve actuator with a direct mounted valvepositioner and a spring cartridge cover assembled in position;

FIG. 3 is a left side elevational view, partly sectional, of FIG. 1illustrating the rotary valve actuator with the spring cartridge coverremoved;

FIG. 4 is a partly sectional view taken generally along section lines4--4 of FIG. 3, illustrating the rotary valve actuator operating arotary shaft for actuating a fluid control valve;

FIG. 5 is a perspective view illustrating a rotatable cylindrical leverutilized in the rotary valve actuator of FIG. 1;

FIG. 6 is a plan view illustrating a bladder used in the rotary valveactuator of the present invention;

FIG. 7 is a sectional view taken along section lines 7--7 of FIG. 6;

FIG. 8 is a sectional elevational view, partly fragmented, illustratingan alternative embodiment of a rotary valve actuator according to thepresent invention wherein the sliding canister and return spring arelocated 90° relative to each other; and

FIG. 9 is a sectional elevational view taken along section lines 9--9 ofFIG. 8.

DETAILED DESCRIPTION

Referring now to the drawings, there is illustrated a rotary valveactuator for fluid control valves, wherein the actuator includes linearto rotary transformation in which tension is always maintained in thelinkage between opposing actuating elements by enabling the actuatingelements to pull against each other in a pull-pull, constant tensionconfiguration. In particular, FIGS. 1-7 illustrate a rotary valveactuator wherein the pull-pull actuating elements are in an in-lineconfiguration. FIGS. 8 and 9 illustrate a rotary valve actuator whereinthe pull-pull actuating elements are in a right-angle configuration.

With reference to FIGS. 1-7, there is illustrated a rotary valveactuator 10 which includes a slidably movable canister 12, an oppositespring cartridge 14 and an intermediately coupled rotatable lever 16,such that the linkage coupling mechanism is always in pull-pull tension.That is, when the canister 12 is being moved in a linear manneroppositely away from the lever 16 in a pulling linkage manner, theopposite spring cartridge 14 is resisting this pulling action of thecanister and is itself exerting a pulling force on the respectivelinkage coupling. Therefore, there is provided a unique "pull-pull"rotary valve actuator 10 which keeps the coupling or respective linkagealways in tension.

The rotatable lever 16 is formed of a hollow hard metal such as steel,cylindrically shaped with opposite flange ends 18, 20 and anintermediate middle portion 22 as shown in FIG. 5. The lever 16 isrotatably mounted within a lower housing 24 and is supported on suitablebearings 25 (see FIG. 1) such that the lever middle portion 22 issupported on bearing support columns 26 in the frame 24. A pair ofsupport columns 28 similar to columns 26 are also provided in an upperhousing 30. As can be seen from FIG. 3, mounting of the lower housing 24to the upper housing 30 captures the lever 16 between opposing supportcolumns 26, 28 so as to rotatably mount the lever 16 within the rotaryvalve actuator 10. Instead of support columns, other lever supportstructure can be provided, such as cast-in wall sections in the housing.

Respective canister linkage mounts 32, 34 project from the respectivelink flanges 18, 20 for mounting respective chain linkages 36, 38 to thecanister 12 (see FIG. 1). A boss 40 projects from the lever middlesection 22 for mounting chain linkage 42 to the spring cartridge 14.

The canister 12 includes a top portion 44 and depending side portions46. A respective canister/chain connector 48 is mounted to respectiveopposite canister sides 46 at one connector end and at the otherconnector end to a respective chain linkage 36, 38.

With reference to FIG. 3, it can be seen that one end of the chain 42 isconnected to the lever boss 40. The other end of chain 42 is mounted toa spring connector 50 which extends from a spring rod 52 within thespring cartridge 14. The spring cartridge 14 also includes opposite endplates 54 and a spring 56 mounted between the end plates 54. As can beseen in FIG. 3, spring rod 52 extends through a suitable aperture in theupper end plate 54 and is mounted by a split rod connector 57 at thegrooved rod end to the lower end plate 54. The upper end of the springcartridge 14 is nested within a spring cavity 58 provided within thehousing 24.

A sealed, expandable bladder unit 60 is provided between canister 12 andan upstanding dome section 62 of the frame 30. The bladder 60 preferablyis a sealed, preformed bladder unit formed of two pieces joined by heatsealing at a joint as disclosed in U.S. application Ser. No. 08/630,529,the disclosure of which is incorporated herein by reference.

Referring to FIGS. 3 and 6, it can be seen that the bladder 60 has anoval shape with an internal surface 64 which fits snugly around the domeshaped projection 62 in the initial deflated bladder condition. As shownin FIGS. 1 and 3, the bladder 60 is mounted on the dome 62 such that theinside bladder surface 64 at the bladder sides is immediately adjacentthe dome 62 exterior sides, and with a bladder bottom surface 66immediately adjacent the dome top surface of the dome 62. A bladder topsurface 68 also lies immediately adjacent the canister top 44.Therefore, the expandable bladder 60 is trapped between the stationaryhousing dome 62 and the slidably movable canister 12.

The bladder may be formed of polyurethane with a cloth backing layer.For lower temperature usage the cloth backing layer is not required. Thecloth backing layer, if used, surrounds the entire bladder and serves toreinforce the bladder material for use at high operating temperatures.At extreme upper temperatures, a thermopolyester plastic material suchas Riteflex may be used for the bladder, with or without a clothreinforcing layer.

The bladder is preferably preformed in the natural state to the smallestchamber size between the canister 12 and the top of dome wall 62. Abladder annular perimeter portion 63 is formed as a convolution of thebladder bottom surface 66. A cloth reinforcing layer can be placed onthe exterior surfaces of the bladder by insertion during injection moldforming of the bladder. Alternatively, after injection molding of thebladder, the cloth can be applied thereto by suitable pressure andtemperature conditions. A urethane layer can be used on a bias cut clothprior to heat bonding to the bladder at a temperature of about 330° F.(166° C.) at 50 psi (345 Kpa) for about 11/2 hours. Instead of applyinga cloth layer on the entire bladder exterior, the cloth may be appliedonly to the annular perimeter portion 63.

The cloth reinforced, preformed bladder is then baked in an oven tostress relieve the material. It has been found that such stressrelieving of the bladder in an oven can be accomplished at about 250° F.(121° C.) for about 24 hours.

To keep the bladder in place during actuator operation, upon assemblyinto the actuator, bonding adhesive beads may be applied above and belowthe bladder two-piece joint at the canister 12. Similarly the bladdercan be bonded with a suitable adhesive to the top of the dome wall 62.

The bladder enables a rolling diaphragm action at the bladder perimeterportion 63 instead of an undesired balloon-type action during expansionof the bladder. As the valve actuator is operated by coupling fluid intothe bladder chamber the bladder perimeter portion 63 in contact with thestationary dome side wall, merely rolls off of engagement with thestationary member while simultaneously increasingly engaging the sidewall of the movable canister.

Thus, the bladder perimeter portion 63 is expanding in going from aninitial unpressurized position to a pressurized position with thebladder perimeter portion merely moving from the inside diameter of thebladder to the outside diameter of the bladder in a rolling fashionplacing the bladder material under tension. This significantly reducesbladder wear, increases the bladder life and enables repeated actuatoroperation over extended operating cycles and wide temperature andpressure ranges.

A bladder inlet tube 70 is inserted within a passageway 72 in housing 30which passageway 72 leads to a connecting passageway 74 having anopening 76 at the bottom of frame 30 as seen in FIG. 3. The inlet tubeincludes a shoulder 71 for mounting an O-ring (not shown) to seal thebladder inlet within the passageway 72.

Passageway opening 76 communicates with an instrument 78, such as apneumatic positioner (see FIG. 2) so that initiating pressurizedexpansion and contraction of the expandable bladder 60 is under controlof the instrument 78 in a known manner. It is understood that thepositioner 78 has been removed from FIG. 3 for convenience inillustrating other components of the rotary valve actuator 10. A plug 80is inserted into the end of the passageway 72 during normal operationsand may be removed from the passageway to gain access to the fluidpassageway 72.

With reference to FIG. 4, there is illustrated the rotary valve actuator10 with a mounting bracket 82 which may be used to mount the valveactuator 10 to a fluid control valve 84, as schematically illustrated inFIG. 4. A valve shaft 86 includes a splined end so as to be rotatablydriven by the rotating lever 16 with very little if any lost motionbetween the rotating lever 16 and the valve shaft 86. Providing thislost motion connection is a splined sleeve 88 (see FIG. 3) havinginterior splines 90 matching the splines on the end of shaft 86. Thesleeve 88 has an outer diameter adapted to the lever bore 92, andfurther includes a flat section 94. A shaft mounting projection 95having an internal threaded bore extends from the lever middle section22 (see FIG. 5). The lever is rotated so the projection 95 is placedopposite an access hole 96 provided in the lower housing 24 as shown inFIG. 3. The sleeve 88 is inserted into the lever bore 92 and the flatsection 94 is positioned opposite the access hole 96 in the lower frame24. A threaded set screw 98 known as a "dog point set screw" includes acorresponding flat end for locking engagement with the flat section 94of the sleeve 88.

With the valve shaft and sleeve positioned within lever bore 92 suchthat the sleeve flat section 94 is aligned with the threaded bore holeprovided through the mounting projection 95 and into the interior of thelever 16 at the bore 92, the set screw 98 threadably engages the bore.The threaded set screw 98 is mounted into the projection 95 until theset screw flat faces lockingly engages the flat section 94 of the sleeve88 to thereby secure the splined sleeve 88, and the splined end of shaft86. This ensures that the valve shaft 86 will rotatably move with thelever 16 with very little, if any, lost motion between the shaft andlever. The sleeve 88 may be split to provide a secure connection to theshaft and lever.

Respective adjustable stops are provided for the movement of the springas well as the sliding canister. With reference to FIG. 3, there isillustrated a canister top position adjustable stop 100 which includes athreaded stop rod 102 threadably engaged within housing 24 and which canbe locked into position by a locking nut 104. A pawl 106 extends fromthe mounting projection 95 so as to rotate with the position of lever16. As can be seen in the notations provided on FIG. 3, linear upwardmovement of the canister 12 during expansion of the bladder 60 rotatesthe lever 16 in a clockwise direction, which is indicated by thereference arrow and notation "C". In FIG. 3 there is also provided anotation indicating the direction of rotation of the lever 16 underpulling action of the spring 56, which reference arrow notation ismarked "S". Accordingly, as the canister 12 moves linearly upwardly inresponse to the expanding bladder, the pawl 106 rotates clockwise untilengaging the end of the stop rod 102. Stop 100 therefore sets theuppermost or top position of the canister 12. The stop position may ofcourse be adjusted by unlocking nut 104 and threadably adjusting rod 102until the desired uppermost canister position is reached.

Referring to FIG. 2, a respective canister bottom position-adjustablestop 108 provided on opposite canister sides includes a threaded stopbolt 110 which is threadably engaged into the housing 30 and can belocked into position using a locking nut 112. The spring 56 tends topull the canister 12 downwardly in FIG. 2, which rotates lever 16 in theillustrated clockwise direction "S" until the bottom end 114 of thecanister engages the threaded stop bolt 110. The stops 108 thereforesets the lowermost or bottom position of the canister 12. The positionof the adjustable stop 108 can readily be changed by unlocking nut 112and threadably adjusting the position of stop bolt 110.

A canister cover 116 is provided for completely covering the canister46, chain connector 48, and adjustable stops 108. The cover 116 may besuitably detachably mounted to the top of the housing 30. Similarly, aspring cartridge cover 118 may be suitably detachably mounted to thelower housing 24 to cover the spring cartridge 14.

With reference to FIG. 2, there is illustrated a feedback linkage 120interconnecting the positioner 78 to the rotatable lever 16. A feedbackarm 122 is connected such as by screws to the lever flange 20 so as torotate with the lever 16. A bent linkage 124 is pivotably connected atone end to the feedback arm 122 and with the other bent linkage endpassing through a slot in the housing 24 to pivotably engage a straightlink arm 126, which in turn is connected to a rotating shaft 128 in thepositioner 78. It is to be understood that the valve positioninginstrument 78 can be a digital valve controller, such as acommunicating, microprocessor-based current to pneumatic instrument. Inaddition to the normal function of converting a input current signal toa pneumatic output pressure, the digital valve controller, using acommunications protocol, can provide easy access to information criticalto process operation. Thus, one can gain information from the principlecomponent of the process, i.e. the fluid control valve 84, using acompatible communicating device at the control valve or at a fieldjunction box, or by using a personal computer or operator counsel withina control room. Alternatively, the instrument can be an analog device ora pneumatic positioner.

As can be seen in FIG. 2, the feedback linkage 120 has one end mountedto the rotating shaft 128 on a positioner 78 and another end mounted viathe feedback arm 122 to the actuator rotating lever 16. Because thelever 16 is interconnected with the rotating valve shaft 86, theposition of the valve shaft is sensed by the positioner 78 through thefeedback linkage 120.

Assembly of the components of the pull-pull rotary valve actuator 10illustrated in FIGS. 1-7 is readily provided in the following manner.Initially, the bladder 60 is snugly mounted atop the dome 62 on theupper housing member 30. The spring cartridge 14 is inserted into thespring cavity 58 on the lower housing 24. The spring cartridge 14 isthen mounted to the lever using appropriate nuts and bolts fasteners tointerconnect the spring chain linkage 42 to the spring connector 50 atone end and to the lever boss 40 at the other end. The two canisterchain links 36, 38 are then connected to the respective lever linkagemounts 32, 34 at one end and to the respective chain connectors 48 atthe other end.

The lever 16 may now be emplaced onto the support columns 26 withsuitable bearings. Next, upper housing 30 is mounted onto the lowerhousing 24 and the housings are secured together. The canister chainlinks 36, 38 are then connected to the respective canister sides usingrespective canister connectors 48 and suitable fasteners. The positioner78 is then mounted to the housing 30 and the feedback linkage 120 isinterconnected between the lever 16 and the positioner. Thereafter, thecovers 116, 118 can be mounted and the mounting bracket 82 as well, ifdesired.

The initial positioning of the canister and spring with respect to theadjustable stops is accomplished as follows. Initially, the spring 56 inthe spring cartridge 14 is precompressed to a predetermined load, andthe spring cartridge is inserted into the housing and connected to thelever as described. Then the spring 56 is preloaded with the linkage sothe spring block 53 on the spring rod 52 is moved off of the top endplate 54 as shown in FIG. 3. Next the bladder is pressurized to move thecanister up sufficiently so the two adjustable stops 108 can be mountedto the housing 30. Both travel stops 110 are then adjusted so that thesliding canister 12 bottoms evenly against the stops before reaching theend of its travel in the downward direction and so there is stilltension maintained in the linkage (see FIG. 3). This sets the canisterbottom position.

Note in FIGS. 2 and 3 that as the spring 56 pulls on the linkage 42 itwill rotate the lever 16 in the reference direction "S" and at the sametime pull the sliding canister 12 downward against the adjustable travelstops 110. Also, FIG. 2 and 3 show the reference direction "C" as theupwardly moving canister 12 pulls on linkage 36, 38 and at the same timecompresses the spring.

When air pressure is supplied through openings 76, passageways 74, 72and into the bladder 70, the pressure will expand the bladder 60 andforce the sliding canister 12 in a linear upward movement whichcorrespondingly rotates the lever 16 in the clockwise direction "C" asshown in FIG. 3. The adjustable stop 100 is adjusted to restrict theupper-most travel of the sliding canister 12 and ensure that the desiredcontrol valve position is reached.

Several advantages are afforded by the pull-pull rotary valve actuator10 as shown in FIGS. 1-7. The linear upward movement of canister 12under the pressure of the expanding bladder 60 rotates the lever 16 andcauses the spring 56 to compress and resist the pull from the slidingcanister. This pull-pull action maintains the chain linkages 36, 38, 42in substantially constant tension i.e., with about only a 3% variance intorque. As the pressure is released from the bladder 60, the spring 56pulls the sliding canister 12 back towards the adjustable stops 110.This pull-pull configuration in the actuator continually takes any lostmotion out of the connecting linkage due to wear caused by cycling, andfurther eliminates the need for precision mated parts, since all matingparts are kept in tension. Also, because the spring 57 is mountedseparately from the sliding canister 12, this allows the lever arm forthe spring (in FIG. 5 measured radially from the centerline of lever 16to the connection point on boss 40) to be shorter for the spring thanthe lever arm for the sliding canister (as measure in FIG. 5 radiallyfrom the centerline of the lever 16 to the connection point on linkagemounts 32, 34). A shorter lever arm reduces the spring travel and inreturn reduces the spring height, making the actuator smaller, lighter,and less costly. Furthermore, it may be noted that since the spring andcanister are substantially in-line at 180° opposite positions withrespect to the lever, and with the connecting linkage to the lever in apull-pull maintained tension condition, the amount of bearing forcesexerted on the support columns 26, 28 and the associated bearings duringdriving rotation of the lever 16 is significantly reduced. Usingflexible linkage chains 36, 38, 42 provides the lever arm (either thespring lever or the canister lever arm) to always be the same respectivedistance from the center of the lever through the 90° rotation of thelever. Thus, the flexible linkage produces constant torque through the90° rotation of the lever and is therefore desired over rigid linkagewhich produces a variable torque over the rotatable position of thelever.

Referring now to FIGS. 8 and 9, there is illustrated an alternativeembodiment of a right angle rotary valve actuator 130 which includesoperating components of the sliding canister, bladder, spring cartridge,and lever identical to the same components with respect to thepreviously described in-line rotary valve actuator 10 of FIGS. 1-7. Ascan be seen from FIG. 8, rather than the in-line configuration of priordescribed rotary valve actuator 10, the rotary valve actuator 130provides the return spring cartridge 14 configured 90° to the centerline of the sliding cartridge 12. This tends to reduce the size, numberof parts and corresponding cost of the actuator. However, because thespring cartridge 14 is angularly positioned with respect to the centerline of the sliding canister 12, (rather than in-line positioning inactuator 10) this creates a diagonal load on the bearings of therotating lever 16 of the actuator 130.

It must be recognized, however, that the rotary valve actuator 130 alsoprovides pull-pull tension of the linkages 36, 38, 42 between thecanister 12, lever 16 and spring cartridge 14, thus maintaining thelinkage in constant tension. Therefore, the many significant advantagesafforded by the pull-pull, in-line rotary valve actuator 10 are alsoaccomplished by the pull-pull, 90° rotary valve actuator 130.

The foregoing detailed description has been given for clearness ofunderstanding only, and no unnecessary limitations should be understoodtherefrom, as modifications will be obvious to those skilled in the art.

What is claimed is:
 1. A rotary valve actuator for fluid control valvescomprising:a housing; a rotatable lever mounted in said housing forrotary movement; a linearly movable actuating member mounted in saidhousing on one side of said rotatable lever; a first linkage connectingsaid linearly movable actuating member to a first point on saidrotatable lever for translating a linear actuating pulling movement ofsaid actuating member to a rotary actuating movement of said rotatablelever; a return spring mounted in said housing on the opposite side ofsaid rotatable lever; and a second linkage connecting said return springto a second point on said rotatable lever for translating a linearreturn pulling movement of said return spring to a rotary actuatingmovement of said rotatable lever and with said first linkage and saidsecond linkage maintained in constant tension.
 2. A rotary valveactuator for fluid control valves comprising:a housing; a rotatablelever mounted in said housing for rotary movement; a linearly movableactuating member mounted in said housing on one side of said rotatablelever; a first linkage connecting said linearly movable actuating memberto a first point on said rotatable lever for translating a linearactuating pulling movement of said actuating member to a rotaryactuating movement of said rotatable lever; a return spring mounted insaid housing on the opposite side of said rotatable lever andsubstantially in-line with said actuating member; and a second linkageconnecting said return spring to a second point on said rotatable leverfor translating a linear return pulling movement of said return springto a rotary actuating movement of said rotatable lever and with saidfirst linkage and said second linkage maintained in constant tension. 3.A rotary valve actuator according to claim 2, wherein said linearlymovable actuating member includes a bladder expandable for moving saidactuating member.
 4. A rotary valve actuator according to claim 3,wherein said linearly movable actuating member includes a canisteroperatively coupled to said bladder for movement during expansion ofsaid bladder.
 5. A rotary valve actuator according to claim 2, whereinsaid first linkage and second linkage comprise flexible members.
 6. Arotary valve actuator according to claim 5, wherein said first linkageand second linkage include flexible chain members.
 7. A rotary valveactuator according to claim 2, including adjustable stops to restrictlinear movement of said actuating member.
 8. A rotary valve actuator forfluid control valves comprising:a housing; a rotatable lever mounted insaid housing for rotary movement; a linearly movable actuating membermounted in said housing on one side of said rotatable lever; a firstlinkage aligned between said linearly movable actuating member and saidrotatable lever and connected to a first point on said rotatable leverfor translating a linear actuating pulling movement of said actuatingmember to a rotary actuating movement of said rotatable lever; a returnspring mounted in said housing on the opposite side of said rotatablelever; and a second linkage connecting said return spring to a secondpoint on said rotatable lever for translating a linear return pullingmovement of said return spring to a rotary actuating movement of saidrotatable lever and with said first linkage and said second linkagemaintained in constant tension, said second linkage angularly disposedwith respect to said first linkage aligned between said linearly movableactuating member and said rotatable lever.
 9. A rotary valve actuatoraccording to claim 8, wherein said second linkage is at right angleswith respect to said first linkage aligned between said actuating memberand said rotatable lever.
 10. A rotary valve actuator according to claim9, wherein said linearly movable actuating member includes a bladderexpandable for moving said actuating member.
 11. A rotary valve actuatoraccording to claim 10, wherein said linearly movable actuating memberincludes a canister operatively coupled to said bladder for movementduring expansion of said bladder.
 12. A rotary valve actuator accordingto claim 8, wherein said first linkage and second linkage compriseflexible members.
 13. A rotary valve actuator according to claim 12,wherein said first linkage and second linkage include flexible chainmembers.
 14. A rotary valve actuator according to claim 8, includingadjustable stops to restrict linear movement of said actuating member.